Fuel injection valve for internal combustion engines

ABSTRACT

A fuel injection valve for internal combustion engines, having an axially movable valve member which, with its end oriented toward the combustion chamber, opens and closes a through flow cross section to at least one injection opening and which, with its end remote from the combustion chamber, protrudes into a fuel-filled spring chamber in which a valve spring is clamped, which acts on the valve member in the closing direction and is supported with its end remote from the valve member against a deflecting piston which, during the supply of high pressure fuel to the fuel injection valve, can be moved a certain distance into the spring chamber and thereby increases the initial stress force of the valve spring, and having a connecting conduit between the spring chamber and a low pressure fuel chamber. The connecting conduit between the spring chamber and the low pressure fuel chamber is embodied as a throttle bore in order to increase the injection opening pressure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is related to a fuel injection valve for internalcombustion engines.

2. Description of the Prior Art

In a fuel injection valve of the type with which is invention isconcerned, which is known from DE 39 00 763, a valve member is guided sothat it can move axially in a guide bore of a valve body. With its endoriented toward the combustion chamber, the valve member controls athrough flow cross section to at least one injection opening into thecombustion chamber of the engine to be supplied. With its end remotefrom the combustion chamber, the valve member protrudes at leastindirectly into a fuel-filled spring chamber in which a valve spring isclamped that acts on the valve member in the closing direction of thethrough flow cross section. This valve spring is supported with its endremote from the valve member against a deflecting piston which, duringthe supply of high fuel pressure to the fuel injection valve, can bemoved a certain distance into the spring chamber and by means of thisinsertion, increases the initial stress force of the valve spring. Thepreinjection in the fuel injection valve is controlled by means of thisincrease in the initial stress force of the valve spring during theinjection phase. The spring chamber containing the valve spring has aconnecting conduit to a low pressure fuel chamber encompassing the valvebody of the fuel injection valve. This low pressure fuel chamber isembodied as an intake chamber for a high pressure fuel pump which,together with the fuel injection valve, constitutes a component and isconnected to the fuel injection valve by means of a clamping nut. Thiscomponent is then inserted into a corresponding receiving opening of thehousing of the engine to be supplied, wherein the control of the highpressure delivery to the high pressure fuel pump and consequently thehigh pressure fuel injection at the fuel injection valve takes place bymeans of an electric control valve, preferably a solenoid valve, whichis connected laterally to the housing of the high pressure fuel pump.

In this connection, however, the fuel injection valve has thedisadvantage that the closing force of the valve spring is not enough toalso produce very high injection opening pressures in the fuel injectionvalve. Furthermore, with the known fuel injection valve, when the valvemember is opened rapidly, an oscillation of the valve spring andconsequently also of the components connected to it—particularly of thevalve member—can occur, which has a disadvantageous effect on theactually prevailing injection opening pressure and as a result, on themetering precision of the injection quantity in the fuel injectionvalve.

SUMMARY OF THE INVENTION

The fuel injection valve for internal combustion engines according tothe invention, has the advantage over the prior art that the closingforces acting on the valve member during the main injection phase can besharply increased while the structural dimensions remain the same. Thisincrease in the closing forces acting on the valve member is achievedthrough the advantageous provision of a throttle between the springchamber and a low pressure fuel chamber, which limits the escape of thefuel disposed in the spring chamber. In this manner, in addition to theincrease of the initial spring stress of the valve spring when thedeflecting piston is inserted into the spring chamber also produces anincrease in the hydraulic closing force, wherein the additionalhydraulic closing force approximately corresponds to the closing forceof the valve spring. Consequently, the closing force can be increasedapproximately by a factor of 2 in comparison to conventional fuelinjection valves. The increased closing forces on the valve memberthereby produce a significant increase in the necessary injectionopening pressure in the fuel injection valve so that an improved fuelinjection characteristic curve can be produced in the injection valve,which has a positive influence on the fuel preparation and combustion inthe combustion chamber of the engine to be supplied, particularly in theengine map region that is sensitive to emissions and consumption. Themagnitude of the additional hydraulic closing force is therebyinfluenced by the throttle diameter, the total stroke of the deflectingpiston, and the shaft diameter of the nozzle needle, wherein theincrease in the injection opening pressure and the maximal injectionpressure during the main injection phase becomes apparent particularlyat low and medium engine speeds. The intensified increase thereby occurswith the small injection quantities, which are important for emissionsmeasurements and in which the peak pressures of the high pressuredelivery pump are hardly ever greater than the injection openingpressures. At the nominal speed and maximal quantity, however, due tothe short cycle times, there is advantageously no significant increasein the maximal injection opening pressure.

Another advantage of providing a throttle opening between the springchamber and the low pressure fuel chamber encompassing the valve holdingbody is the damping effect of the hydraulic pressure in the springchamber, which suppresses oscillations of the valve spring andconsequently fluctuations of the injection opening pressure.

The pressure in the spring chamber, which only decreases slowly due tothe throttle action, furthermore advantageously encourages the closingof the valve member with increasing force as the speed increases, whichis particularly advantageous due to the short diversion times at highspeeds. In addition, less cavitation is produced in the high pressureregion after the closing of the valve member, which reduces thesubsequent filling stroke in it. This permits the reduction of noiseemission and the risk of an undesirable reopening of the valve member.

The provision, according to the invention, of a throttle relief bore ofthe spring chamber in connection with a deflecting piston that reducesthe volume of the spring chamber is shown in the exemplary embodiment ofa so-called unit fuel injector, but can also be used in other injectionsystems which provide a deflecting piston in the spring chamber of thefuel injection valve.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will be apparent from thedetailed description contained hereinbelow, taken in conjunction withthe drawing, in which the single is a longitudinal section through thepart of the above-described fuel injection valve for internal combustionengines that is essential to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The exemplary embodiment of the fuel injection valve according to theinvention shown in FIG. 1 indicates the fuel injection valve 1 in acomponent with a high pressure fuel pump 3, which component has anelectric control valve 5 disposed on it and is inserted as a componentinto a housing 7 of the engine to be supplied.

The fuel injection valve 1 has a valve body 9 which, with its one end,protrudes into a combustion chamber, not shown in detail, of the engineto be supplied and with its other end, with the interposition of anintermediary disk 11, is clamped axially against a valve holding body13. This axial clamping is achieved by means of a clamping nut 15, whichencompasses a shoulder on the valve body 9 and which is screwed into athread of a housing 17 of the high pressure fuel pump 3. The valve body9 of the fuel injection valve 1 also has a guide bore 19 in which apiston-shaped valve member 21 is guided so that it can move axially. Ina known manner, on its end oriented toward the combustion chamber, thevalve member 21 has a valve sealing face 23 which it uses to cooperatewith a valve seat face 25 at the closed-end of the guide bore 19 inorder to control an injection opening cross section. Downstream of thesealing cross section between the sealing face 23 and the valve seatface 25, injection openings 27 lead away from the valve seat face 25 andfeed into the combustion chamber of the internal combustion engine. Thevalve member 21 also has a pressure shoulder 29 on its shaft, pointingin the direction of the opening stroke, with which it protrudes into apressure chamber 31 which is formed by a cross sectional enlargement ofthe guide bore 19. This pressure chamber extends to the valve seat face25 and can be filled with high pressure fuel by means of a high pressurefuel conduit 33. On its end remote from the combustion chamber, thevalve member 21 also has a pressure pin 35, which passes through theintermediary disk 11 and feeds into a cross-sectionally enlarged springchamber 37 in the valve holding body 13. In this connection, a lowerspring plate 39 is provided on the end of the pressure pin 35 orientedtoward the spring chamber and a valve spring 41, which is clamped in thespring chamber 37, rests against the other side of this spring plate andthereby acts on the valve member 21 in the closing direction toward thevalve seat face 25. On the other end, this valve spring 41 is supportedagainst an upper spring plate 43 which, on its side remote from thespring, rests against a deflecting piston 45.

With its pressure pin 35, the valve member 21 protrudes into afuel-filled damping chamber 47, which is defined by a stationaryshoulder 49 formed by the end face of the intermediary disk 11 and thisshoulder thereby forms a stroke stop for an annular shoulder 51 on thevalve member 21. Between the wall of the damping chamber 47 and thepressure pin 35, a throttle cross section is formed, which is embodiedas a flat ground area 53 and is used to connect the damping chamber 47to the spring chamber 37. The flat ground area 53 on the pressure pin 35has an axial spacing from the annular shoulder 51 on the valve member 21in the vicinity of which the pressure pin 35 corresponds to the diameterof the receiving opening in the intermediary disk 11 so that a controledge 55 is formed whose passage beyond the shoulder 49 triggers theclosing of the hydraulic damping chamber 47.

The housing 17 of the high pressure fuel pump 3 is clamped axiallyagainst the valve holding body 13 via an intermediary piece 57 by meansof the clamping nut 15. The high pressure fuel pump 3 has a pump piston61 that can be moved axially in a cylinder bore 59 and, with itsinserted end face, defines a pump work chamber 63 in the cylinder bore59. For the high pressure fuel delivery, the pump piston 61 is driven toreciprocate via a tappet push rod 65 by means of a motor-driven camdrive that is not shown in detail. The supply of low pressure fuel takesplace by way of a supply line 67 in the motor housing 7 into an annularchamber 69 encompassing the fuel injection valve 1, which chamber isconnected by means of filter openings 71 in the clamping nut 15 to anintake chamber 73 that is formed between the clamping nut 15 and thevalve holding body 13. From this intake chamber 73, a first control line75 leads to the electric control valve 5, which is embodied in a knownmanner as a solenoid valve and, in a manner not shown in detail,controls the overflow of fuel into a second control line 77 as afunction of the operating parameters of the engine to be supplied, bymeans of an electric control unit. This second control line 77 likewisepasses through the housing 17 of the high pressure fuel pump 3 and feedsinto the pump work chamber 63. In addition, a bore 79 leads from thepump work chamber 63 and feeds into a through opening in theintermediary piece 57, which thereby constitutes a hydraulic workchamber 81. In addition, the bore 79 is connected by means of connectingconduits 83 to the high pressure fuel conduit 33 which passes throughthe valve body 9 and the valve holding body 13 and thus produces thehydraulic connection between the pump work chamber 63 and the pressurechamber 31 and also the valve seat 25.

The hydraulic work chamber 81 has two different diameters, wherein afirst smaller diameter region 85 is continuously connected to the pumpwork chamber 63 of the high pressure fuel pump 3 by way of the bore 79.A second larger diameter region 87 of the hydraulic work chamber 81 canbe connected to the pump work chamber 63 only after a through flow crosssection is opened by means of the stroke motion of the deflecting piston45. To this end, the deflecting piston 45 has two different hydraulicforce introduction surfaces, of lwhich a first smaller forceintroduction surface 89 defines the smaller diameter hydraulic workchamber part 85. A second larger force introduction surface 91 is formedon an annular collar 93 on the deflecting piston 45 and defines thelarger diameter region 87 of the hydraulic work chamber 81. With itslower annular end face remote from the force introduction surface 91,the annular collar 93 constitutes a stop face 95, which cooperates witha stationary stroke stop face 97 in order to limit the stroke motion ofthe deflecting piston 45. The stroke stop face 97 is connected to theend face of the valve holding body 13 remote from the combustionchamber. With its lower end remote from the pump work chamber 63, thedeflecting piston 45 protrudes into the spring chamber 37 and isattached to the upper spring plate 43 there.

In order to influence the opening stroke characteristic curve andconsequently the characteristic curve of the injection jet in the fuelinjection valve 1, a connecting conduit is embodied as a throttle bore99 between the spring chamber 37 and the intake chamber 73 thatconstitutes a low pressure fuel chamber, and the additional hydraulicclosing force on the fuel injection valve 1 can be adjusted by means ofthe diameter of this throttle bore.

The fuel injection valve for internal combustion engines according tothe invention functions in the following manner. During the intakestroke of the high pressure fuel pump 3, when the pump piston 61 ismoved upward, fuel is aspirated into the pump work chamber 63 from theintake chamber 73 via the first control line 75, the open electriccontrol valve 5, and the second control line 77. The valve member 21 ofthe fuel injection valve 1 is kept in the closed position against thevalve seat 25 by means of the valve spring 41. With the beginning of thedownwardly directed delivery stroke of the pump piston 61 of the highpressure fuel pump 3, first a part of the fuel from the pump workchamber 63 is conveyed back into the intake chamber 73 via the samepath. Depending on the operating parameters of the engine to besupplied, the electric control valve controls the beginning time andalso the ending time of the high pressure delivery of the high pressurefuel pump 3 to the fuel injection valve 1. The high pressure fueldelivery and thereby the fuel injection in the fuel injection valve 1are initiated by the closing of the through flow cross section betweenthe control lines 75 and 77 at the electric control valve 5. As a resultof this, with the downwardly directed delivery stroke of the pump piston61, a high fuel pressure is built up in the pump work chamber 63, whichtravels via the bore 79, the conduit 83, and the high pressure fuelconduit 33 to the pressure chamber 31 in the fuel injection valve 1.After the necessary injection opening pressure is exceeded there, thefuel injection valve opens in a known manner by means of the valvemember 21 lifting up from the valve seat 25 so that the high pressurefuel travels from the pressure chamber 31 via the injection openings 27and reaches injection into the combustion chamber of the internalcombustion engine.

The fuel injection in the fuel injection valve according to theinvention is divided into a preinjection quantity and a main injectionquantity, wherein during the preinjection phase, the valve member 21only travels a limited opening stroke path initially, which is limitedby the control edge 55 on the valve member 21 traveling past theshoulder surface 49 of the intermediary disco 11 as a result of whichthe damping chamber 47 in the fuel injection valve 1 is closed so thatthe closing force on the valve member 21 increases. At the same time,with the currently prevailing high injection pressure, the deflectingpiston 45 begins to lift up from its seat and is moved in the directionof the spring chamber 37 as a result of the high fuel pressure currentlyacting on the first force introduction surface 89 and, after thedeflecting piston 45 lifts up from the seat, acting on the second forceintroduction surface 91. This movement of the deflecting piston 45toward the spring chamber 37 produces an increase of the initial springstress of the valve spring 41 and also, because of the throttled escapeof fuel from the spring chamber 37, produces an increase in thehydraulic pressure in the spring chamber 37 due to its volume reductionso that the total closing forces currently acting on the valve member 21exceed the prevailing opening force and thus move the valve member 21back against its valve seat 25 so that the preinjection phase is ended.Then, in the continued course of the high pressure fuel delivery strokeof the pump piston 61, the high fuel pressure in the pump work chamber63 and in the connected chambers of the fuel injection valve 1 increasesagain until the injection opening pressure necessary for the maininjection is achieved. This injection opening pressure necessary for themain injection is determined by the currently increased spring force ofthe valve spring 41, the total stroke of the deflecting piston 45, andthe throttle diameter of the throttle bore 99, which determine theadditional hydraulic closing force in the spring chamber 37. After theinjection opening pressure necessary for the main injection is exceeded,then the valve member 21 in turn lifts up from the valve seat 25 so thatthe main injection quantity then reaches injection in a known manner viathe injection openings 27. By means of the above-mentioned additionalhydraulic closing pressure on the valve member 21, it is thus possibleto approximately double the injection opening pressure necessary for themain injection so that the main injection quantity can be injected witha higher injection pressure and consequently in a shorter time,particularly at low and medium speeds. This main injection phaseadvantageously begins shortly before the deflecting piston 45 reachesthe stroke stop 97. The main injection is ended in a known manner by theopening of the electric control valve 5, which opens the hydraulicconnection between the control lines 77 and 75 again so that the highfuel pressure in the pump work chamber 63 and in the high pressure linesinside the fuel injection valve 1 collapses. In this connection, theadditional hydraulic closing pressure in the spring chamber 37, whichcan only decrease relatively slowly as a result of the throttle 99,encourages a rapid and reliable closing of the fuel injection valve,i.e. a rapid movement of the valve member 21 back into contact with thevalve seat face 25.

The magnitude of the additional hydraulic closing force in the springchamber 37 and its pressure decrease can be adjusted as a function ofthe total stroke of the deflecting piston 45 and the shaft diameter ofthe valve member 21 by means of the dimensioning of the throttle bore99, wherein with a stroke path of the deflecting piston 45 ofapproximately 0.5 to 1 mm, the diameter of this throttle bore 99preferably lies in a range from 0.4 to 1.2 mm.

Consequently, with the fuel injection valve according to the invention,the injection opening pressure in the fuel injection valve during themain injection phase can be significantly increased in comparison toconventional fuel injection valves without having to carry outsignificant changes in the design of the fuel injection valve and inparticular of the valve spring 41.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodiments arethereof possible within the spirit and scope of the invention, the afterbeing defined by the appended claims.

What is claimed is:
 1. In a fuel injection valve for internal combustionengines, having an axially movable valve member (21) which, with its endoriented toward the combustion chamber, opens and closes a through flowcross section to at least one injection opening (27) and which, with itsend remote from the combustion chamber, at least indirectly protrudesinto a fuel-filled spring chamber (37) in which a valve spring (41) isclamped, which acts on the valve member (21) in the closing directionand is supported with its end remote from the valve member against adeflecting piston (45), which piston, during the supply of high pressurefuel to the fuel injection valve, can be moved by a certain stroke pathinto the spring chamber (37) and thereby increases the initial stressforce of the valve spring (41), and having a connecting conduit betweenthe spring chamber (37) and a low pressure fuel chamber (73), theimprovement wherein the connecting conduit between the low pressure fuelchamber (73) and the spring chamber (37) is embodied as a throttle (99),and wherein a high pressure pump (3) that delivers high pressure fuelconstitutes a component together with the fuel injection valve (1) andthis component is adapted to be inserted into a housing (7) of theengine to be supplied, and wherein an electric control valve (5) isdisposed on the high pressure pump (3) in order to control the highpressure delivery of the high pressure pump (3).
 2. The fuel injectionvalve according to claim 1, wherein the throttle (99) is embodied as athrottle bore, whose diameter preferably lies in a range between 0.4 and1.2 mm.
 3. The fuel injection valve according to claim 2, whereinstarting from the spring chamber (37), the throttle bore (99) feeds intothe low pressure fuel chamber (73), which encompasses the fuel injectionvalve.
 4. it a fuel injection valve for internal combustion engines,having an axially movable valve member (21) which, with its end orientedtoward the combustion chamber, opens and closes a through flow crosssection to at least one injection opening (27) and which, with its endremote from the combustion chamber, at least indirectly protrudes into afuel-filled spring chamber (37) in which a valve spring (41) is clamped,which acts on the valve member (21) in the closing direction and issupported with its end remote from the valve member against a deflectingpiston (45), which piston, during the supply of high pressure fuel tothe fuel injection valve, can be moved by a certain stroke path into thespring chamber (37) and thereby increases the initial stress force ofthe valve spring (41), and having a connecting conduit between thespring chamber (37) and a low pressure fuel chamber (73), theimprovement wherein the connecting conduit between the low pressure fuelchamber (73) and the spring chamber (37) is embodied as a throttle (99),wherein on its end remote from the combustion chamber, the valve member(21) has a pressure pin (35) which protrudes into a fuel-filled dampingchamber (47), which is defined by a stationary shoulder (49) thatconstitutes a stroke stop for an annular shoulder (51) on the valvemember (21), and wherein between the wall of the damping chamber (47)and the pressure pin (35) a throttle cross section is formed, whichfeeds into the spring chamber (37) and can be closed during the strokemotion of the valve member (21).
 5. In a fuel injection valve forinternal combustion engines, having an axially movable valve member (21)which, with its end oriented toward the combustion chamber, opens andcloses a through flow cross section to at least one injection opening(27) and which, with its end remote from the combustion chamber, atleast indirectly protrudes into a fuel-filled spring chamber (37) inwhich a valve spring (41) is clamped, which acts on the valve member(21) in the closing direction and is supported with its end remote fromthe valve member against a deflecting piston (45), which piston, duringthe supply of high pressure fuel to the fuel injection valve, can bemoved by a certain stroke path into the spring chamber (37) and therebyincreases the initial stress force of the valve spring (41), and havinga connecting conduit between the spring chamber (37) and a low pressurefuel chamber (73), the improvement wherein the connecting conduitbetween the low pressure fuel chamber (73) and the spring chamber (37)is embodied as a throttle (99), wherein the deflecting piston (45) isguided in a hydraulic work chamber (81), which has two differentdiameters, wherein a first smaller diameter region (85) continuouslycommunicates with a pump work chamber (63) of the high pressure pump (3)and a second larger diameter region (87) can be connected to the pumpwork chamber (63) only after the opening of a through flow cross sectionthrough a stroke motion of tho deflecting piston (45) and that thedeflecting piston (45) has two different hydraulic force introductionsurfaces of which a first smaller force introduction surface (89)adjoins the first smaller diameter region (85) of the hydraulic workchamber (81) and a second larger force introduction surface (91) isdisposed in the second larger diameter region (87) of the hydraulic workchamber (81).
 6. In a fuel injection valve for internal combustionengines, hasting an axially movable valve member (21) which, with itsend oriented toward the combustion chamber, opens and closes a throughflow cross section to at least one injection opening (27 and which, withits end remote from the combustion chamber, at Least indirectlyprotrudes into a fuel-filled spring chamber (37) in which a valve spring(41) is clamped, which acts on the valve member (21) in the closingdirection arid is supported with its end remote from the valve memberagainst a deflecting piston (45), which piston, during the supply ofhigh pressure fuel to the fuel injection valve, can be moved by acertain stroke path into the spring chamber (37) and thereby increasesthe initial stress force of the valve spring (41), and having aconnecting conduit between the spring chamber (37) and a low pressurefuel chamber (13), the improvement wherein the connecting conduitbetween the low pressure fuel chamber (73) and the spring chamber (37)is embodied as a throttle (99), wherein a high pressure pump (3) thatdelivers high pressure fuel constitutes a component together with thefuel injection valve (1) and this component is adapted to be insertedinto a housing (7) of the engine to be supplied, and wherein an electriccontrol valve (5) is disposed on the high pressure pump (3) in order tocontrol the high pressure delivery of the high pressure pump (3), andwherein the deflecting piston (45) is guided in a hydraulic work chamber(81), which has two different diameters, wherein a first smallerdiameter region (85) continuously communicates with a pump work chamber(63) of the high pressure pump (3) and a second larger diameter region(87) can be connected to the pump work chamber (63) only after theopening of a through flow cross section through a stroke motion of thedeflecting piston (45) and that the deflecting piston (45) has twodifferent hydraulic force introduction surfaces of which a first smallerforce introduction surface (89) adjoins the first smaller diameterregion (85) of the hydraulic work chamber (81) and a second larger forceintroduction surface (91) is disposed in the second larger diameterregion (87) of the hydraulic work chamber (81).
 7. The fuel injectionvalve according to claim 5, wherein the deflecting piston (45) has anannular collar (93) that adjoins the hydraulic work chamber (81) andwhose annular end face oriented toward the pump work chamber (63)constitutes the second larger force introduction surface (91) and whoseannular end face remote from the pump work chamber (63) constitutes astop face (95) that cooperates with a stationary stroke stop face (97)in order to limit the stroke motion of the deflecting piston (45). 8.The fuel injection valve according to claim 5, wherein on its end remotefrom the pump work chamber (63), the deflecting piston has an upperspring plate (43) that protrudes into the spring chamber (37) andconstitutes an adjustable counter support for the valve spring (41).